Exhaust manifolds for internal combustion engines may be exposed to high thermal loads. Exhaust manifolds that are integrated into cylinder heads (IEM cylinder heads) may experience particularly high thermal loading due to the heat transfer characteristics of the integrated design. For example, IEM cylinder heads may channel exhaust to a collector and a single exhaust port, which experiences a high thermal load during operation of the vehicle.
Thermal loading of an IEM and neighboring components can be reduced by incorporating coolant jackets into the cylinder head. The coolant jackets with, a coolant core formed therein, can reduce the thermal stresses on the cylinder head caused by heat generated during engine operation. For example, a cylinder head having an integrated exhaust manifold is disclosed in U.S. Pat. No. 7,367,294. Upper and lower coolant jackets encompass a major portion of the cylinder head to remove heat from the cylinder head via heat exchange with a circulated liquid coolant.
However, the inventors herein have recognized issues with the above described approach. For example, during some conditions, steam may accumulate in portions of the coolant passages, such as in portions of the coolant chamber positioned vertically at a top of the passages in the IEM and proximate to the exhaust port. Accumulation of steam and/or other gases causes the liquid coolant to lose contact with at least a top wall of the coolant jacket. Under such conditions, the temperature of cylinder head can increase in a region of the cylinder head proximal the accumulated steam, particularly in a region proximal to the exhaust collector and the exhaust port. As a result, the cylinder head and/or other cylinder components may thermally degrade. Further, exhaust gases may be insufficiently cooled and downstream engine or vehicle components, such as a turbocharger and/or an emission control system, may also thermally degrade.
As such, various example systems and approaches to address the above issues are described herein. In one example, an engine cooling system comprises a cylinder head including an integrated exhaust manifold that directs exhaust gases to an exhaust port; a coolant passage surrounding the exhaust manifold and having a coolant jacket above the exhaust port; and a degas port positioned along the top side of the coolant jacket, the degas port fluidically coupled to the coolant passage at an inlet of the degas port. The degas port may be further coupled to a degas bottle at an outlet of the degas port. The degas bottle may permit pressure relief via a pressure release valve and return of liquid coolant to a coolant passage of a radiator. Furthermore, a temperature sensor may be included in the coolant jacket at a position near exhaust collector and/or the exhaust port to communicate a temperature signal to a controller of the vehicle. If the temperature signal is greater than a predetermined threshold, an overheating indication may be provided and/or corrective action may be taken by the engine control system.
In this way, the cooling system may provide improved engine overheating protection. For example, steam accumulated at the top of the coolant chamber can be vented from the coolant chamber to the degas bottle. As a result, the liquid coolant may maintain contact with the coolant jacket wall, and continue heat exchange in order to decrease thermal stress on the cylinder head by generating a convective coolant circuit. Thus, the degas port along the top side of the coolant jacket may decrease the likelihood of thermal degradation of the cylinder head and cool exhaust gas to decrease the likelihood of thermal degradation on downstream components, such as the turbocharger, the emission control system, etc. Further, the temperature sensor may provide an improved indication of over-temperature conditions in the exhaust system. Thus, performance and life of the engine, turbocharger, and emission control system can be improved.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.